Liquid processing industries, especially those in food processing such as milk homogenization, are often troubled with vibration in processing pipelines where transfer pumps are utilized. Two distinctly different types of pressure fluctuations are created by most types of transfer pumps: low frequency fluctuations due to the pulsating flow and a higher frequency acoustic "ring", or water hammer, associated with sudden changes in flow due to the pump's valve action or to process valve action. The magnitude and frequency of the pressure fluctuations due to these two types of flow pulsations is determined by the number and displacement of the pump plungers and the speed of the pump.
The water hammer pulses occur at the beginning of each suction stroke when the discharge valve closure abruptly stops the backflow into the plunger chamber. At the end of the pumping stroke the discharge valve is still open, and there is a momentary backflow into the plunger chamber as the plunger starts on the suction stroke. When the discharge valve closes, there is a sudden deceleration of the fluid moving toward the valve. The fluid begins to "back up" at the discharge valve, resulting in a pressure wave which moves out toward the process equipment at the speed of sound (normally about 4,000 feet per second in the fluid medium) and, subsequently, is reflected repeatedly throughout the system resulting in a ringing effect.
For sanitary application, the flow paths through an acoustic dampener must act to sweep the unit of old product, not leaving any product to stagnate. Such a design allows for what is known as "clean in place" performance.
An object of this invention is to provide a pulsation dampener and acoustic attenuator suitable for sanitary applications.
A further object of this invention is to provide a hydraulic dampener which may be readily disassembled to facilitate inspection, cleaning or replacement of a diaphragm within the assembly.